New EPA administrator Lisa Jackson said in an interview with the Associated Press that the agency would soon issue a long-awaited finding on whether greenhouse gases pose a significant threat to human health and welfare. If the forthcoming "endangerment finding" concludes that GHGs do indeed pose such a threat, it would trigger EPA's obligation to regulate them as pollutants as under the Clean Air Act (CAA).

Unsurprisingly, such a finding would be a significant reversal of the Bush-era EPA's general refusal to regulate GHGs under the CAA, notwithstanding numerous petitions from states and environmental groups seeking such regulation. The Supreme Court's 2007 decision in Massachusetts v. EPA rejected EPA's stated grounds for declining to enact GHG regulations for automobiles under the Clean Air Act, and compelled the agency to issue an endangerment finding. Instead of following the Court's directive, EPA instead issued an Advanced Notice of Proposed Rulemaking in July 2008, inviting public comment on GHG regulation under the CAA but stating in no uncertain terms the then-administrator's view that many features of the CAA made it "the wrong tool" for the regulation of GHG emissions.

Since the confirmation of Administrator Jackson, a coalition of states has again urged EPA to move quickly to make an endangerment finding and to regulate GHG emissions from automobiles.